Coreless induction heater and method of making same



Dec. 28, 1948. B. RONAY l 2,457,179 ;J CORDLESS INDUCTION HEATER AND ETI-.10D oF MAKING SAME Filed sept. 18, 1945 i i 2 sheets-sneer 1 i Fig' 2 Dec. 28, 1948. B. RONAY 2,457,179

CORELESS INDUCTION HEATER AND METHOD OF MAKING SAME Filed Sept. 18, 1945 2 Sheets-Sheet 2 HELE 5%-?. gqfjg 3mm Bela. ECH-Lal.;

Patented Dec. 28, 1.948

CORELESS INDUCK'yIION HEATER AND METHOD F MAKING SAIVIE,

Bela Ronay, Annapolis, Md.

Application September 18 1945, Serial No. 617,156'

t (c1. 21a-47) (Granted under the act of March s, 1883, as Y( 6 Claims.

amended April 30, 1928,;V 370 O. G. 757) The present invention relates to improvements in coreless induction heaters and method of making the same and more particularly to improvements in a coreless induction heater of the type disclosed in my Patent No. 2,176,103 dated October 17, 1939.

An object of the present invention is the provision of means enabling a ready assembly of the coreless induction heater and providing a strong and durable construction.

Another object is to provide an improved method of fabrication and assembly of the -coreless induction heater coil or coil sections which requires a minimum of tooling `and a. minimum manufacturing cost.

A further object is the provision of a plurality of heater coil sections with means for readily connecting and disconnecting the sections.

"A still further object is to provide means for varying the number and spacing yof the turns or units of the coil in a coil section and for varying the pitch of the turns or -units to control and regulate the application of heat to the article Ibeing heated, at different points along the length of the article.

Other objects and advantages of the invention will be made more apparent by the following description in connection with the accompanying drawings which are exemplary and in which:

Fig. 1- is an end elevation of a coreless induction heater according to the present invention, applied to an object t-o be heated.

Fig. 2 is a plan View of the coreless induction heater.

Fig. 3 is a fragmentary sectional view of the structure substantially on line 3 3 of Fig. 2 and showing the connection between the tie rods of adjacent sections of the heating coil.

Fig. 4 is an elevation partly in section of the U-shaped coil unit or portion at one stage in its manufacture or fabrication according to the present invention.

Fig. 5 is an edge elevation of the assembly of Fig. 4.

Fig. 6 is an elevation partly in section of the completed U-shaped coil unit or member with connecting blade or strap assembled therewith.

Fig. '7 is an edge elevation of the U-shaped coil unit or portion which is slotted to receive an end of the connecting blade or strap.

Figs. 8, 9, and 10 are diagrams showing that the coil sections may be connected in series parallel as in Fig. 8, in parallel as in Fig. "9, and in direct series as are the end or outer sections in Fig. 10, depending on the requirements for heat 2 `distribution and on the number of transformers available.

Fig. 11 is a fragmentary plan view similar to Fig. 2 of a portion of the coil and apparatus of the present invention adjusted and varranged for lcontrolled or regulated heating.

Referring to the drawing-s showing a coreless induction heater constructed in accordance with lthe invention, a coil or conductor unit of U-shape is shown in Figs. 6 and 1, which is designed to be assembled with a plurality of like U-shaped units in spaced parallel relation and with bent or offset connecting blades or straps I, as indicated in Fig. 2, and together forming a heating coil adapted to embrace an article to be heated, in the manner set forth in my Patent No. 2,176,103. One end of each blad-e or strap I is pivoted at one end of a U- shaped unit with the other en-d of the blade or strap received in the slotted :opposite end of the next adjacent, U-shaped unit, thus forming a coil or helix.

l The individual U-shaped members or units of the coil in my said patent are disclosed as lpreferably constructed -of metal tubing bent into U- sh-aped and flattened to a total thickness of substantially three times that of the wall of the tubing, thus permitting the slotted ends of the U- shaped members or units to receive the ends of the straps or blades i in the manner of a knife switch blade.

' The fabrication -to form and atten lthe U- shaped units in the manner described in my said patent requires lconsiderable tooling which in turn makes for a substantial manufacturing cost.

-The .present invention is designed to provide an effective assembly and meth-od including novel features of construction and fabrication which involve a minimum of tooling and manufacturing cost 4and which is .adjustable to provide for varying conditions and heating requirements.

According to the present invention, the individual U-shaped coil unit is formed by using a straight tube section 2 and two tube sections 3 and 4 intermediately bent or oil'set at approximately 20 from straight, and two 90 elbows 5 and 6,' all desirably of metal such as soft copper. The elbows may be standard, commercial, forged elbows and must be fully annealed before assembly. The tube sections desirably are brazed or soldered into the elbows as seen in Fig. 4, and the U-shaped unit thus assembled is then kflattened throughout to make the total thickness of the ends of the flattened U-shaped unit substantially equal to three times the wall thicknessl of said ends as indicated in Fig. 7, with the elbows flattened proportionately. As is apparent from Fig. 6, the 90 elbows `of Fig. 4 are spread to more than 90 in the process of flattening them and the bent tube sections 3 and 4 are somewhat straightened in the flattening process to about from straight. As is also apparent from Figs. 1 and 6, thre degree4 of bend of the flattened bent tube sections 3 and 4 'of the iiattene'd unit, is such as to substantially compensate for the greater than 90 degree elbows of the flattened unit, the end portions of said bent sections being substantially parallel in said U-shaped unit. The ends of the flattened U-shaped unit of Fig. 6, are then slotted as indicated land provided with'the pivoted straps or blades I and the U-s'hap'edunits are then assembled into a group or groups in the manner indicated in Fig. 2.

As indicated in Figs. 2 and 3 the individual U shaped units are grouped in lsections held together by tie rods 1 provided with tubular insulating members 8 between the rods and the U- shaped conductor coil units or members. Insulating spacer washers Il are provided between the adjacent U-shapecl coil units or members.

The Vtie rod connections between the units are provided at a plurality of points on the units, preferably three, as shown. Openings I0 are provided in the `UV-shapedunits for receiving the tie rods and tubular 4insulating members.

Centering or `positioning adjusting screws II like Ithose disclosed in my Patent 2,176,103, are provided threaded into extension -members I2 provided onthe ends of the terminal tie rods, and are vdesigned to engage the article A to be heated.

According to the fpresent invention the extension `members I2 are formed integral with a nut or `head I3 on the end of the tie rod. The nut or `head I3 engages a washer I4 which in turnengeges the end of the tubular insulating member 8.

The washer -I4 is `of greater diameter than thatof the tubular insulating -member `8 and greaterlthan the diameter -of the opening I0 in the U-shaped coil unit, so that Ian `insulating spacer or spacers lmay be interposed between the washer` I4 `and the coil unit.

The washers I4 are preferably of `the `same diameter as the-insulating spacers '9 `in order to securely retain the end insulating spacers 9 in place. The washers I4 are held to the ends of the tubular insulators Bfby enlargements at each end of vthe ytie rods, nin `the lformofheads or nuts `on the rods.

In the embodiment shown irl-Figs. 2 -and 3,the enlargements on the ends of `the rods of adjacent groups orsections'are formed as pin and socket connectionsto permit ready centering and assemblingof the groups or sections of heating coil as an interconnected induction heating assembly. A `soeltetnut or head I5 may desirably belprovideden the endof onetie rod to receive a nut or head zI6 providing atpin or projection on -the adjacent tie rod.

The coil 4siecticms or groupsof 'Ushaped--units may comprisefanyl-suitable number of VU'shaped units, by `way of` exampleffour units being shown as cemprisingthe end groups or `sections andsix `units comprising the centersection.

Figc-2 and `the diagrams of Figs. 8,19, l0 indicate thatthe coil sections or` groups of Ushaped units may-beconnected in fseries. as indicated in Fig. 2, or in series` parallel as indicatedin Figs, 8 `and 10, or in `parallel fasindicated in Fig. r9, -depending upon the requirements for heat i distribution and on the number of transformers available. Fig. 8 indicates a four section heater. In Figs. 2, 9, and 10, three section heaters are indicated.

For example, the connection indicated in Fig. 10 is particularly applicable to a cylindrical object such as the journal portion of a heavy shaft. For such use the center coil section or group Which contains a sufficient number of U-shaped units or turns to cover the entire length of the journal portion `of the shaft, is desirably connected directly to a power source of suitable capacity. The two, shorter, outer coil sections or groups, each comprising a lesser number of U- shaped units or coil turns, are shown in Fig. 10 as bei-ng connected in series and energized by another power source desirably of smaller capacity. The 'end or outer sections, thus connected in series, serve to prevent loss of heat into the adjacent portions of the object being heated, and therefore require only enough energy input to compensate for the heat loss through conduction through the portions of the object adjoining the ends of the portion desired to be heated by the center section.

If, in addition, it is desired to maintain a uniform temperature throughout the entire length `of the heated portion of the object, such as a shaft journal, this is accomplished according to the present invention, by the provision of narrower insulating spacers 9c between the U-shaped coil units at the end zones of a coil section, such as the central coil section or group, and the provision `of Wider insulating spacers 9b between the U-shaped coil units at the central zone of the coil section or group. This is indicated in Fig. 11, includingthe provision of connecting blades Ia of reduced angular offset at the end zones of the coil section and connecting blades Ib `of increased bend or angular offset at the central zone of the coil section. Thus there is provided a decrease of the pitch of the U turns or coils at the end zones of the coil section and an increase of the pitch at the central zone of the coil section to control or regulate the heating of or to apply a uniform heating temperature to the object Within the `particular coil section, the heat input being thereby increased at the end zones and decreased at the central zone of the coil section. Preferably the connecting blades or straps are adapted to be readily bent to provide variations in the angular offset thereof for this purpose.

By the provision, according to the invention of ithe insulating spacers oi various Widths and the U-shaped coil units having connecting blades orlstraps of v-arious degrees of angular offset and adjustable by bending to change the angular offset, means are provided to regulate and control the application of heat in any zone or portion of any coil section or group of coil units, and thus to `control the heat imparted to any part of the portion of an object Within the coil section.

VSuiiicient length of tie rod is provided in each group or section to provide room for varying the spacing between the coil units -by the removal or insertion of insulating spacers 9 at the ends of the `tie rods-and tubular insulating members and the'removal and insertion of spacers 9 of various widths between the units.

The temperature of each heated section can be regulated automatically by use of controlling devices (not shown) attached by thermocouples fastened to the sections.

The electrical connections with the coil units yor ysections are `die.granunatically illustrated in Fig. 2 and may be made in any suitable manner, such, for example, as is disclosed in my said Patent 2,176,103.

It will be understood that vari-ous changes in the construction and details of the apparatus and method illustrated and described herein may be made without departing from the spirit of the invention and it is not intended to limit the invention other than by the terms of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A coreless induction heater coil having U- shaped units secured together in mutually insulated relation with means extending between them to form the coil, each of said units consisting of a straight and two bent or 4offset tube sections connected by two elbows, said assembled unit being in a flattened condition and in substantially U-shape, the flattened tubing being of a thickness substantially three times its wall thickness, and said elbows being in a proportionately flattened `condition and greater than 90 degrees, the degree of bend of the said bent sections of said flattened unit being about 15 degrees and such as to substantially compensate for the greater than 90 degree elbows, end portions of said bent sections Ibeing substantially parallel to each other in said U-shaped unit.

2. Steps in a method of making a coreless induction heater coil unit comprising connecting a straight and two bent tube members by inserting and brazing them into two 90 forged annealed elbows, flattening said assembled tubular unit to substantially three times the wall thickness of the tube members, and decreasing the angle of offset of the bent tube members, and flattening said elbows proportionately and increasing their angles to greater than 90, and thereby spreading the ends of said unit to substantially U- shape.

3. Steps in a method of making a coreless induction heater coil unit comprising connecting a straight and two bent tube members having an offset of substantially 20 degrees, by inserting and brazing them into two 90 forged annealed elbows, flattening said assembled tubular unit to substantially three times the wall thickness of the tube members, and thereby decreasing the angle of offset of the bent tube members to substantially 15 degrees, and flattening said elbows proportionately and increasing their angles to greater than 90 and thereby spreading the ends of said unit to substantially U-shape.

4. A coreless induction heater coil having U- shaped units secured together in mutually insulated relation with means extending between them to form the coil, each of said units consisting of a straight and two bent or offset tube sections connected by two elbows, said assembled unit being in a flattened condition and in substantially U-shape, and said elbows being in a proportionately flattened condition and greater than degrees, the degree of bend of the said bent sections of said flattened unit being such as to substantially compensate for the greater than 90 degree elbows, end portions of said bent sections being substantially parallel to each other in said U-shaped unit.

5. lSteps in a method of making a coreless indu-ction heater coil unit comprising connecting a straight and two bent tube members by inserting and brazing them into two 90 degree forged annealed elbows, flattening said assembled tubul-ar unit, and decreasing the angle of offset of the bent tube members, and attening said elbows proportionately and increasing their angles to greater than 90 degrees, and thereby spreading the ends of said unit to substantially U-shape.

6. Steps in a method of making a coreless induction heater coil unit comprising connecting a straight and two bent tube members by inserting and brazing them into two 90 degree forged annealed elbows, flattening said assembled tubular unit, and decreasing the angle of bend of the bent tube members and flattening said elbows proportionately and increasing their angles to greater than 90 degrees, and thereby spreading the ends of said unit to substantial parallelism and providing substantially U-shape of said unit, the resultant angle of bend of said bent tube members and the resultant angle of said elbows substantially compensating each other and resulting in said parallelism.

BELA RONAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 648,481 Berresford May 1, 1900 1,646,498 Seede Oct. 25, 1927 1,718,806 Witting June 25, 1929 1,791,934 Northrup Feb. 10, 1931 1,839,802 Northrup Jan. 5, 1932 1,946,876 Northrup Feb. 13, 1934 2,176,103 Ronay Oct. 17, 1939 2,202,758 Denneen et al May 28, 1940 2,299,934 Sherman et al Oct. 27, 1942 2,303,408 Soderholm Dec. 1, 1942 2,335,495 Fink Nov. 30, 1943 2,383,992 ySherman Sept. 4, 1945 

